Process for the production of water-soluble fluorine-containing vinyl ethers

ABSTRACT

The present invention relates to a method for producing a water-soluble fluorine-containing vinyl ether which comprises subjecting a fluorine-containing 2-alkoxypropionic acid derivative represented by the following general formula (I):  
                 
 
(wherein A represents —OM 1  or —OM 2   1/2 , and M 1  represents an alkali metal and M 2  represents an alkaline earth metal; X represents a halogen atom; Y 1  and Y 2  are the same or different and each represents a fluorine atom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkyl group; n represents an integer of 0 to 3, and n of Y 1 s may be the same or different; m represents an integer of 1 to 5, and m of Y 2 s are the same or different; and Z represents a hydrophilic group) to thermal decomposition at a temperature of not lower than 50° C. but lower than 170° C. in the presence of a coordinating organic solvent to give a water-soluble fluorine-containing vinyl ether represented by the general formula (II):  
                 
 
(wherein Y 1 , Y 2 , Z, n and m are as defined above), 
 
     said coordinating organic solvent having a coordinating property with an ion of said M 1  or an ion of said M 2  said coordinating organic solvent being in an amount of 10 to 1,000 parts by mass per 100 parts by mass of the fluorine-containing 2-alkoxypropionic acid derivative.

TECHNICAL FIELDS

The present invention relates to a method for producing a water-solublefluorine-containing vinyl ether from fluorine-containing2-alkoxypropionic acid derivatives in good yields.

BACKGROUND ART

Hydrophilic group-terminated fluorine-containing vinyl ethers can beused, either as such or after protection of the terminal hydrophilicgroup by fluorination or by esterification, amidation or imidation, forthe production of copolymers by polymerization with another fluoroolefinand/or the like.

The copolymers obtained can have salt-forming hydrophilic groups and,therefore, the use thereof as ion exchange membranes in saltelectrolysis, chemical sensors, separation membranes, fuel cells and soforth is under investigation. They can also be utilized as superstrongacid catalysts in the form of powders as such, or in lithium cells andso on.

As a method for obtaining water-soluble fluorine-containing vinylethers, there is disclosed, in WO 98/43952 pamphlet, a thermaldecomposition method which comprises heating, for decarboxylation, afluorine-containing 2-alkoxypropionic acid derivative with carboxylgroup being in the form of a metal salt. This thermal decompositionmethod known in the art has a problem in that a side reaction occurs,namely oligomers are formed from the fluorine-containing2-alkoxypropionic acid derivative.

As regards the reaction conditions for this thermal decomposition, WO01/28989 pamphlet discloses that the reaction should preferably becarried out at 170 to 230° C. using 1 to 5 parts by weight of a catalysthaving a coordinating property with a metal ion per 100 parts by weightof the fluorine-containing 2-alkoxypropionic acid derivative.

Under such conditions, however, the byproduct oligomers are formed inlarge amounts and the yield of the desired product thus decreases. Incarrying out the reaction on a large scale using a large-sized reactor,in particular, a long time is required for raising the temperature andfor lowering the temperature, whereby the production of oligomersfurther increases. Thus, there is a problem that such conditions aredifficult to apply on a commercial scale.

The water-soluble fluorine-containing vinyl ethers, which are the targetproducts to be obtained by this thermal decomposition reaction, occur ashigh-boiling salts and, therefore, the distillation method cannot beused as the method of purifying them. A promising method isrecrystallization. However, it is not easy to crystallize thewater-soluble fluorine-containing vinyl ethers in the presence of alarge amount of oligomers, which are uncrystallizable and thus renderthe purification by recrystallization difficult to achieve.

SUMMARY OF THE INVENTION

In view of the above-discussed state of the art, it is an object of thepresent invention to provide a method for producing a water-solublefluorine-containing vinyl ether in good yields from fluorine-containing2-alkoxypropionic acid derivatives.

The present invention relates to a method for producing a water-solublefluorine-containing vinyl ether which comprises subjecting afluorine-containing 2-alkoxypropionic acid derivative represented by thefollowing general formula (I):

(wherein A represents —OM¹ or —OM² _(1/2), and M¹ represents an alkalimetal and M² represents an alkaline earth metal; X represents a halogenatom; Y¹ and Y² are the same or different and each represents a fluorineatom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkylgroup; n represents an integer of 0 to 3, and n of Y¹s may be the sameor different; m represents an integer of 1 to 5, and m of Y²s are thesame or different; and Z represents a hydrophilic group) to thermaldecomposition at a temperature of not lower than 50° C. but lower than170° C. in the presence of a coordinating organic solvent to give awater-soluble fluorine-containing vinyl ether represented by thefollowing general formula (II):

(wherein Y¹, Y², Z, n and m are as defined above),

said coordinating organic solvent having a coordinating property with anion of said M¹ or an ion of said M² and

said coordinating organic solvent being used in an amount of 10 to 1,000parts by mass per 100 parts by mass of the fluorine-containing2-alkoxypropionic acid derivative.

In the following, the present invention is described in detail.

DETAILED DISCLOSURE OF THE INVENTION

The method for producing a water-soluble fluorine-containing vinyl ethercomprises subjecting a fluorine-containing 2-alkoxypropionic acidderivate represented by the above general formula (I) to thermaldecomposition.

The fluorine-containing 2-alkoxypropionic acid derivative represented bythe above general formula (I) is such one that A in the above generalformula (I) represents —OM¹ or —OM² _(1/2), wherein M¹ represents analkali metal and M² represents an alkaline earth metal. The alkali metalM¹ is not particularly restricted but includes, among others, Li, Na, Kand Cs. The alkaline earth metal M² is not particularly restricted butincludes, among others, Mg and Ca. Preferably, A is —OM¹, and M¹ is Na,which is commercially inexpensive.

In the above general formula (I), X represents a halogen atom. Thehalogen atom is not particularly restricted but may be any of fluorine,chlorine, bromine and iodine atoms.

In the above general formula (I), Y¹and Y² are the same or different andeach represents a fluorine atom, a chlorine atom, a perfluoroalkyl groupor a fluorochloroalkyl group. The perfluoroalkyl group is notparticularly restricted but maybe, for example, a trifluoromethyl groupor a pentafluoroethyl group. The fluorochloroalkyl group is notparticularly restricted but may be, for example, a difluorochloromethylgroup. Preferably, Y¹ is a trifluoromethyl group and Y² is a fluorineatom.

In the above general formula (I), n represents an integer of 0 to 3. Then of Y¹s may be the same or different. For the fluorine-containing2-alkoxypropionic acid derivative having a lot of hydrophilic groups perunit weight thereof, the above-mentioned n is preferably 0 or 1, morepreferably 0.

In the above general formula (I), m represents an integer of 1 to 5. Them of Y²s may be the same or different. As the above-mentioned mincreases, the acid strength increases but the number of the hydrophilicgroups per unit weight of the fluorine-containing 2-alkoxypropionic acidderivative decreases. Therefore, the above-mentioned m is preferably 2.

In the above general formula (I), Z represents a hydrophilic group. Thehydrophilic group is not particularly restricted but may be, forexample, —COOM³, —OSO₃M³, —SO₃M³, —O₂PM³, —OP (OM³)₂, —O₂P (OM³), —OPO(OM³)₂, —PO₂ (OM³), —PO (OM³)₂, —COOM⁴ _(1/2), —OSO₃M⁴ _(1/2), —SO₃M⁴_(1/2), —O₂PM⁴ _(1/2), —OP (OM⁴ _(1/2))₂, —O₂P (OM⁴ _(1/2)) —OPO (OM⁴_(1/2))₂, —PO₂ (OM⁴ _(1/ 2)), —PO (OM⁴ _(1/2))², or a substitutedammonio group forming a salt with a conjugate base of an inorganic acidor fatty acid (its substituents being two or three alkyl groups whichmay be the same or different).

The above-mentioned M³ represents an alkali metal or hydrogen atom orNR¹R²R³R⁴, and R¹, R², R³ and R⁴ are the same or different and eachrepresents a hydrogen atom or an alkyl group containing 1 to 4 carbonatoms. The alkali metal includes, among others, those given above by wayof example referring to M¹. The above-mentioned M⁴ is an alkaline earthmetal, and the alkaline earth metal includes, among others, those givenabove by way of example referring to M².

The term “substituted ammonio group” as used herein means a groupconstituted of a nitrogen atom and two or three alkyl groups, which arethe same or different and are covalently bound to that nitrogen atom atsites other than the site represented by —(CFY²)_(m)— in the abovegeneral formula (I).

The substituted ammonio group is not particularly restricted but may be—NR⁵R⁶H or —NR⁵R⁶R⁷ (in which R⁵, R⁶ and R⁷ may be the same or differentand each represents an alkyl group), for instance. The above substitutedammonio group forms a salt with a conjugated base of a monobasic orpolybasic inorganic acid or fatty acid. The inorganic acid is notparticularly restricted but includes, among others, hydrochloric acid,phosphoric acid, sulfuric acid and nitric acid. The fatty acid is notparticularly restricted but includes, among others, formic acid, aceticacid and propionic acid.

In the above general formula (I), Z is preferably —SO₃M³ or —SO₃M⁴_(1/2), more preferably —SO₃M³, still more preferably —SO₃Na.

The fluorine-containing 2-alkoxypropionic acid derivative represented bythe above general formula (I) is preferably one in which, in the abovegeneral formula (I), Z is —SO₃M³ , A is —OM¹ or —OM² _(1/2), Y¹ is atrifluoromethyl group, Y² is a fluorine atom and m is 2. Morepreferably, in the above general formula (I), Z is —SO₃Na, A is —Ona, Xis a fluorine atom, Y² is a fluorine atom, n is 0 and m is 2.

The method for preparing the fluorine-containing 2-alkoxypropionic acidderivative represented by the above general formula (I) is notparticularly restricted but, for example, any of the methods known inthe art can be employed. Among the fluorine-containing 2-alkoxypropionicacid derivatives represented by the above general formula (I), thosecompounds represented by the following general formula:

(wherein X, Y¹, Y², n, m, M¹ and M² are as defined above) can beobtained by neutralizing or saponifying the corresponding compoundsrepresented by the following general formula:

(wherein Al represents an alkoxyl group or a halogen atom, A² representsa halogen atom; X, Y¹, Y², n and m are as defined above) using aneutralizing reagent.

The method for producing a water-soluble fluorine-containing vinyl etheraccording to the present invention comprises subjecting afluorine-containing 2-alkoxypropionic acid derivative represented by theabove general formula (I) to thermal decomposition in the presence of acoordinating organic solvent to give the corresponding water-solublefluorine-containing vinyl ether represented by the general formula (II).

The coordinating organic solvent has a coordinating property with theion of the above-mentioned M¹ or the ion of the above-mentioned M². Inthe method for producing a water-soluble fluorine-containing vinyl etheraccording to the present invention, the above coordinating organicsolvent exhibits a decarboxylation reaction-promoting catalytic actionby coordinating the ion of M¹ or the ion of M² which thefluorine-containing 2-alkoxypropionic acid derivative of the abovegeneral formula (I) has.

The coordinating organic solvent is not particularly restricted but maybe any of those having a coordinating property with an ion of M¹ or anion of M². Preferably, it comprises an aprotic polar organic solvent.The aprotic polar organic solvent is not particularly restricted butincludes, among others, ether solvents, sulfolane, hexamethylphosphorictriamide, acetonitrile, dimethylformamide, dimethyl sulfoxide, ethylacetate, tetramethylurea and the like. One or two or more of these maybe used singly or in combination.

The ether solvent is not particularly restricted but includes, amongothers, glyme-based compounds, diethyl ethers, diisopropyl ethers,tetrahydrofuran, dioxane, anisole, and crown ethers. These may be usedsingly or two or more of them may be used in combination.

The above-mentioned glyme-based compounds are hydrocarbon-based ethercompounds represented by the general formula:R—O

CH₂CH₂—O

Rwherein R represents —C_(p)H_(2p+1), p represents an integer of 1 to 5and q represents an integer of 1 to 10.

As the above-mentioned glyme-based compounds, there may be mentioneddimethoxyethane, monoethylene glycol dimethyl ether, diethylene glycoldimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycoldimethyl ether, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether and diethoxyethane, among others. These may be usedsingly or two or more of them may be used in combination.

The above-mentioned aprotic organic polar solvent is preferably aglyme-based solvent, more preferably diethylene glycol dimethyl ether.

Preferably, the aprotic polar organic solvent has a water content notexceeding 250 ppm so that the yield of the water-solublefluorine-containing vinyl ether may be increased. The aprotic polarorganic solvent is required to have the water content within the aboverange only at least on the occasion of thermal decomposition. Morepreferred is diethylene glycol dimethyl ether with a water content notexceeding 250 ppm.

In cases where a low-boiling solvent such as ethyl acetate ortetrahydrofuran is used as the coordinating organic solvent, suchequipment as a pressure reaction apparatus becomes necessary forcarrying out the thermal decomposition reaction at a temperature notlower than the boiling point of such solvent; however, the purificationof the water-soluble fluorine-containing vinyl ether is easier than inthe case of using a glyme-based solvent.

In carrying out the thermal decomposition in the practice of the presentinvention, the coordinating organic solvent itself may be used also as adispersion medium. It is also possible, however, to use an inert solventtogether with the coordinating organic solvent. Preferred as the inertsolvent are fluorocarbons, which can be readily dehydrated, so that theyield of the water-soluble fluorine-containing vinyl ether may beincreased. The fluorocarbons are not particularly restricted butinclude, among others, fluorocarbons and fluorochlorocarbons, which maybe etherified. Among them, perfluorocarbons and perfluorochlorocarbonsare preferred. The inert solvent may comprise one single species or twoor more species.

The coordinating organic solvent is used in an amount of 10 to 1,000parts by mass per 100 parts by mass of the fluorine-containing2-alkoxypropionic acid derivative. Within the above range, the thermaldecomposition initiation temperature becomes low, hence the byproductformation can be suppressed. When that amount is less than 10 parts bymass, the thermal decomposition reaction may proceed slowly and/or thethermal decomposition may proceed only to an unsatisfactory extent. Whenthe amount exceeds 1,000 parts by mass, a large reaction vessel becomesnecessary and this is disadvantageous from the industrial viewpoint. Apreferred lower limit is 30 parts by mass, and a preferred upper limitis 300 parts by mass.

The method for producing a water-soluble fluorine-containing vinyl etheraccording to the present invention is characterized in that theabove-mentioned fluorine-containing 2-alkoxypropionic acid derivative issubjected to thermal decomposition at a temperature not lower than 50°C. but lower than 170° C. in the presence of the above-mentionedcoordinating organic solvent to give the corresponding water-solublefluorine-containing vinyl ether represented by the general formula (II).

When the thermal decomposition according to the present invention iscarried out at temperatures not lower than 170° C., byproducts areformed in large amounts. The byproducts have not yet been clearlyidentified but probably are, among others, oligomers represented by theformula:

(wherein k represents an integer of 2 to 15, and Y¹, Y²,Z, n and m areas defined above) as formed by the reaction of the fluorine-containing2-alkoxypropionic acid derivative with the water-solublefluorine-containing vinyl ether or by the mutual reaction of moleculesof the water-soluble fluorine-containing vinyl ether. As the byproductformation increases, the yield of the water-soluble fluorine-containingvinyl ether decreases. In particular, when the reactor size increases, along time is required for raising and lowering the temperature and,accordingly, the water-soluble fluorine-containing vinyl ether isexposed to high temperatures for a prolonged period of time, with theresult that the byproduct formation is still increased.

As for the method of purifying the water-soluble fluorine-containingvinyl ether, recrystallization may be a promising method. Since,however, the byproducts are not crystallizable, it is difficult tocrystallize the water-soluble fluorine-containing vinyl ether in thepresence of a large amount of such byproducts.

When, in carrying out the thermal decomposition according to the presentinvention, the temperature is lower than 50° C., time is required forthe thermal decomposition or the thermal decomposition may fail toproceed, although the byproduct formation mentioned above can besuppressed. The thermal decomposition is preferably carried out at atemperature not lower than 50° C. but lower than 150° C. Preferably, thethermal decomposition is carried out after thoroughly drying, fordehydration, the fluorine-containing 2-alkoxypropionic acid derivativeand catalyst, and the inert solvent to be used if desirable.

The thermal decomposition reaction time in the practice of the presentinvention is preferably 10 to 600 minutes after arrival at the intendedreaction temperature, although it depends on the temperature at whichthe thermal decomposition is carried out. If the reaction time isshorter than 10 minutes, the thermal decomposition may be incomplete. Amore preferred lower limit is 30 minutes, and a more preferred upperlimit is 300 minutes.

In the practice of the present invention, the fluorine-containing2-alkoxypropionic acid derivative preferably has a water content notexceeding 0.1% by mass. When the water content is higher than 0.1% bymass, the fluorine-containing 2-alkoxypropionic acid derivative reactswith the water in certain cases to give, as a byproduct, a compoundrepresented by the general formula:

(wherein X, Y¹, Y², Z, n and m are as defined above) and, accordingly,the yield of the water-soluble fluorine-containing vinyl ether tends todecrease. It is only required that the fluorine-containing2-alkoxypropionic acid derivative has a water content within the aboverange at least on the occasion of carrying out the thermaldecomposition.

The water-soluble fluorine-containing vinyl ether obtained by the methodfor producing a water-soluble fluorine-containing vinyl ether accordingto the present invention is represented by the above general formula(II) given herein above. In the above general formula (II), Y¹, Y², Z, nand m are as defined herein above referring to the above general formula(I).

According to the method of the present invention, byproduct formationcan be inhibited by subjecting the fluorine-containing 2-alkoxypropionicacid derivatives to thermal decomposition at a temperature not lowerthan 50° C. but lower than 170° C. using the above-mentionedcoordinating organic solvent, therefore the water-solublefluorine-containing vinyl ethers can be obtained in good yields from thefluorine-containing 2-alkoxypropionic acid derivatives.

The water-soluble fluorine-containing vinyl ethers can be polymerized,either as such or after protection of the terminal hydrophilic group byfluorination or by esterification, amidation or imidation, together withanother fluoroolefin, for instance, to give copolymers.

The copolymers obtained, which have salt-forming hydrophilic groups, canbe adequately used as electrolyte membranes such as ion exchangemembranes or diaphragms. As for the ion exchange membranes, they can beutilized in salt electrolysis, chemical sensors, separation membranes,fuel cells and so forth. The copolymers obtained can also be used asmacromolecular superstrong acid catalysts in the form of powders assuch, or in lithium cells or the like, in the form of liquids.

BEST MODES FOR CARRYING OUT THE INVENTION

The following examples illustrate the present invention in furtherdetail. These examples are, however, by no means limitative of the scopeof the present invention.

PRODUCTION EXAMPLE 1 Synthesis of a fluorine-containing2-alkoxypropionic acid derivative

-   1.1) A 6-liter glass-lined pressure-resistant autoclave was charged    with SO₃ (2 liters) freshly prepared by distillation of Sulfan    (stabilized sulfuric anhydride; product of Nisso Metallochemical    Co.), the inside space atmosphere was purged with pure nitrogen gas    for substitution therewith, and tetrafluoroethylene was then charged    into the autoclave under pressure, upon which the exothermal    reaction started immediately. The reaction was continued while    maintaining the temperature at 40-60° C. and the pressure at 0.1to    0.2MPa. After 40 minutes, when the product amount increased to 5.2    liters and the absorption of tetrafluoroethylne was no longer    observed, the reaction was terminated by cooling. The reaction    product was a colorless, transparent liquid, which, upon    distillation, was found to be almost pure tetrafluoroethane    β-sultone.-   1.2) A 6-liter glass-lined pressure-resistant autoclave was charged    with 400 g of potassium fluoride thoroughly dried at 300° C. and    then tightly closed under nitrogen streams. Then, 1 liter of    diethylene glycol dimethyl ether was charged into the autoclave, and    the sultone (1 liter) obtained in the step 1.1) was added dropwise.    A marked exothermic reaction took place, and it was confirmed by    ¹⁹F—NMR analysis that the isomerization reaction to FSO₂CF₂COF had    been completed almost quantitatively although the formation of free    FSO₂CF₂CF₂OK was also observed.-   1.3) The product FSO₂CF₂COF obtained using the same reaction    apparatus and conditions as used in the step 1.2) was added, under    pressure at −10° C., and hexafluoropropylene oxide [HFPO] gas was    added to a pressure of 0.2 MPa, whereupon the exothermal reaction    started immediately. While the temperature was adjusted to −15 to    −5° C., the reaction was continued at a pressure of 0.1 to 0.2 MPa    for 3 hours. Thereafter, the rate of pressure dropping decreased, so    that the reaction was interrupted, and the residual gas was    discharged. The volume of the product was 2.7 liters, and the    product consisted of a yellow upper phase and a colorless lower    phase. Upon distillation, 90% by volume of the product was found to    be the HFPO (one mole) adduct, namely the compound:    FSO₂CF₂CF₂OCF (CF₃) COF.    In addition, the formation of a slight amount of FSO₂CF₂COF and the    HFPO (two moles) adducts was observed.-   1.4) The compound obtained in the step 1.3) was neutralized with a    20% (by mass) aqueous solution of sodium hydroxide for quantitative    conversion to the corresponding fluorine-containing    2-alkoxypropionic acid derivative. Thus was obtained a 36% (by mass)    aqueous solution of a compound represented by the formula:    NaOC (O) CF (CF₃) OCF₂CF₂SO₃Na.

The aqueous solution obtained was removed of the insoluble NaF byfiltration and then dried at 80° C. for 36 hours and then further at120° C. for 12 hours.

EXAMPLE 1

A 20-liter glass vessel equipped with a stirrer was charged with thefluorine-containing 2-alkoxypropionic acid derivativeNaOC(O)CF(CF₃)OCF₂CF₂SO₃Na (6.4 kg) obtained in Production Example 1 and5.3 kg of diethylene glycol dimethyl ether (83 parts by mass per 100parts by mass of the fluorine-containing 2-alkoxypropionic acidderivative). The vessel was heated by means of a mantle heater. Uponarrival of the inside temperature at 100° C., the generation of CO₂started. The inside temperature was then slowly raised to 140° C. After180 minutes of heating, the CO₂ generation subsided and, therefore, theheating was discontinued. Pure water (6 liters) was added to thereaction mixture obtained for dissolving the same, the insoluble sodiumfluoride was filtered off, and the remaining diethylene glycol dimethylether layer was extracted with 7 portions of chloroform to give anaqueous solution.

The thus-obtained aqueous solution was subjected to ¹⁹F-NMRspectrometry, and a comparison was made between the large peak at about−83.3 ppm (relative to CDCl₃) due to the underlined fluorine atoms of—OCF ₂CF₂— in the water-soluble fluorine-containing vinyl etherCF₂=CF—OCF ₂CF₂—SO₃Na and a number of byproduct-due small peaks at −78to −85 ppm. It was found that the ratio [water-solublefluorine-containing vinyl ether]:[byproducts] was 100:9. The aqueoussolution obtained was evaporated to dryness; the product was readilycrystallized and could be purified by recrystallization.

COMPARATIVE EXAMPLE 1

A 20-liter glass vessel equipped with a stirrer and a reflux condenserwas charged with 6.4 kg of the fluorine-containing 2-alkoxypropionicacid derivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na obtained in ProductionExample 1 and, as inert solvents, 17.7 kg of Cl(CF₂CFCl)₃Cl and 240 g ofdiethylene glycol dimethyl ether (3 parts by mass per 100 parts by massof the fluorine-containing 2-alkoxypropionic acid derivative). Thevessel was heated by means of a mantle heater. Upon arrival of theinside temperature at 180° C., the generation of CO₂ started. After 7hours of heating under refluxing conditions (inside temperature 203°C.), the CO₂ generation suppressed and, therefore, the heating wasdiscontinued. After cooling, the reaction mixture obtained was filtered,and the solid matter was washed with HCFC-225. The solid matter thusobtained was dissolved in water, and the insoluble sodium fluoride wasfiltered off to give an aqueous solution.

The thus-obtained aqueous solution was subjected to ¹⁹F-NMRspectrometry, and a comparison was made between the large peak at about−83.3 ppm (relative to CDCl₃) due to the underlined fluorine atoms of—OCF ₂CF₂— in the water-soluble fluorine-containing vinyl etherCF₂=CF—OCF ₂CF₂—SO₃Na and a number of byproduct-due small peaks at −78to −85 ppm. It was found that the ratio [water-solublefluorine-containing vinyl ether] :[byproducts] was 100:102. The aqueoussolution obtained was evaporated to dryness; the product only became athick syrup-like substance but could not be purified byrecrystallization.

EXAMPLE 2

A 500-ml SUS stainless steel autoclave equipped with a reflux condenserwas charged with the fluorine-containing 2-alkoxypropionic acidderivative NaOC(O)CF(CF₃)OCF₂CF₂SO₃Na (80 g) obtained in ProductionExample 1 and 130 g of ethyl acetate (163 parts by mass per 100 parts bymass of the fluorine-containing 2-alkoxypropionic acid derivative). Thecontents were heated to 145° C. by means of a heater and stirred. TheCO₂ generated was discharged through the reflux condenser so that theautoclave inside pressure might be maintained at a level not exceeding0.1 MPa. After 5 hours, no increase in inside pressure was observed anylonger, so that the autoclave was allowed to cool. All the internal gaswas discharged at around room temperature. The reaction mixture wasfiltered, and the filtrate was concentrated under reduced pressure togive a white solid. The solid obtained was subjected to ¹⁹F-NMRspectrometry, whereby it was confirmed that the water-solublefluorine-containing vinyl ether CF₂═CF—OCF₂CF₂—SO₃Na was the mainproduct ([water-soluble fluorine-containing vinyl ether]:[byproducts]=100:9).

EXAMPLE 3

A 300-ml SUS 316 stainless steel autoclave was charged with 81 g of thefluorine-containing 2-alkoxypropionic acid derivativeNaOC(O)CF(CF₃)OCF₂CF₂SO₃Na obtained in Production Example 1 and 88 g oftetrahydrofuran (109 parts by mass per 100 parts by mass of thefluorine-containing 2-alkoxypropionic acid derivative) . The contentswere heated to 140° C. by means of a heater and stirred for 3 hours. Theautoclave inside pressure arrived at a maximum of 1.4 MPa. The autoclavewas allowed to cool, and all the internal gas was discharged at aroundroom temperature. The reaction mixture was filtered, and the filtratewas concentrated under reduced pressure to give a white solid. The solidobtained was subjected to ¹⁹F-NMR spectrometry, and it was confirmedthat the water-soluble fluorine-containing vinyl etherCF₂═CF—OCF₂CF₂—SO₃Na was the main product ([water-solublefluorine-containing vinyl ether]:[byproducts] =100:11).

INDUSTRIAL APPLICABILITY

The method for producing a water-soluble fluorine-containing vinyl etheraccording to the present invention, which has the constitution describedabove, makes it possible to obtain water-soluble fluorine-containingvinyl ethers in good yields from the corresponding fluorine-containing2-alkoxypropionic acid derivatives.

1. A method for producing a water-soluble fluorine-containing vinylether which comprises subjecting a fluorine-containing 2-alkoxypropionicacid derivative represented by the following general formula (I):

(wherein A represents —OM¹ or —OM² _(1/2), and Mrepresents an alkalimetal and M² represents an alkaline earth metal; X represents a halogenatom; Y¹ and Y² are the same or different and each represents a fluorineatom, a chlorine atom, a perfluoroalkyl group or a fluorochloroalkylgroup; n represents an integer of 0 to 3, and n of Y¹ s may be the sameor different; m represents an integer of 1 to 5, and m of Y²s may be thesame or different; and Z represents a hydrophilic group) to thermaldecomposition at a temperature of not lower than 50° C. but lower than170° C. in the presence of a coordinating organic solvent to give awater-soluble fluorine-containing vinyl ether represented by thefollowing general formula (II):

(wherein Y¹, Y², Z, n and m are as defined above), said coordinatingorganic solvent having a coordinating property with an ion of said M¹ oran ion of said M² and said coordinating organic solvent being in anamount of 10 to 1,000 parts by mass per 100 parts by mass of saidfluorine-containing 2-alkoxypropionic acid derivative.
 2. The method forproducing a water-soluble fluorine-containing vinyl ether according toclaim 1, wherein the hydrophilic group is —COOM³, —OSO₃M³, —SO₃M³,—O₂PM³, —OP(OM³)₂, —O₂P(OM³), —OPO(OM³)₂, —PO₂(OM³), —PO(OM³)₂, —COOM⁴_(1/2), —OSO₃M⁴ _(1/2), —SO₃M⁴ _(1/2), —O₂PM⁴ _(1/2), —OP(OM⁴_(1/2))_(2, —O) ₂P(OM⁴ _(1/2)), —OPO(OM⁴ _(1/2))₂, —PO₂(OM⁴ _(1/2)),—PO(OM⁴ _(1/2))₂, or a substituted ammonio group forming a salt with aconjugate base of an inorganic acid or fatty acid (its substituentsbeing two or three alkyl groups which are the same or different),wherein M³ represents an alkali metal, a hydrogen atom or NR¹R²R³R⁴ inwhich R¹, R², R³ and R⁴ are the same or different and each represents ahydrogen atom or an alkyl group containing 1 to 4 carbon atoms, and M⁴represents an alkaline earth metal.
 3. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 1,wherein the thermal decomposition is carried out at a temperature notlower than 50° C. but lower than 150° C.
 4. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 1,wherein the coordinating organic solvent is in an amount of 30 to 300parts by mass per 100 parts by mass of the fluorine-containing2-alkoxypropionic acid derivative.
 5. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 1,wherein the coordinating organic solvent comprises an aprotic polarorganic solvent.
 6. The method for producing a water-solublefluorine-containing vinyl ether according to claim 5, wherein theaprotic polar organic solvent is an ether solvent, sulfolane,hexamethylphosphoric triamide, acetonitrile, dimethylformamide, dimethylsulfoxide, ethyl acetate and/or tetramethylurea.
 7. The method forproducing a water-soluble fluorine-containing vinyl ether according toclaim 6, wherein the ether solvent is a glyme-based solvent, a diethylether, a diisopropyl ether, tetrahydrofuran, dioxane, anisole and/or acrown ether.
 8. The method for producing a water-solublefluorine-containing vinyl ether according to claim 7, wherein theglyme-based solvent is dimethoxyethane, diethoxyethane, monoethyleneglycol dimethyl ether, diethylene glycol dimethyl ether, triethyleneglycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyleneglycol monomethyl ether and/or diethylene glycol monoethyl ether.
 9. Themethod for producing a water-soluble fluorine-containing vinyl etheraccording to claim 5, wherein the aprotic polar organic solvent is aglyme-based solvent.
 10. The method for producing a water-solublefluorine-containing vinyl ether according to claim 5, wherein theaprotic polar organic solvent has a water content not exceeding 250 ppm.11. The method for producing a water-soluble fluorine-containing vinylether according to claim 5, wherein the aprotic polar organic solvent isdiethylene glycol dimethyl ether.
 12. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 11,wherein the diethylene glycol dimethyl ether has a water content notexceeding 250 ppm.
 13. The method for producing a water-solublefluorine-containing vinyl ether according to claim 1, wherein thefluorine-containing 2-alkoxypropionic acid derivative represented by thegeneral formula (I) has a water content not exceeding
 0. 1% by mass. 14.The method for producing a water-soluble fluorine-containing vinyl etheraccording to claim 1, wherein n is 0 or
 1. 15. The method for producinga water-soluble fluorine-containing vinyl ether according to claim 2,wherein Z is —SO₃M³ or —SO₃M⁴ _(1/2)
 16. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 2,wherein Z is —SO₃M³ , A is —OM¹ or —OM² _(1/2), Y¹ is a trifluoromethylgroup, Y² is a fluorine atom and m is
 2. 17. The method for producing awater-soluble fluorine-containing vinyl ether according to claim 16,wherein n is 0.